The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Motor oil is a type of liquid oil used for lubrication by various types of motors. In particular, internal combustion engines use motor oil to provide lubrication between mechanical components. The motor oil also serves as a cooling system to the engine. The motor oil dissipates heat generated by friction between the mechanical components.
Oil viscosity is the ability of oil to flow and is expressed as a proportionality constant between the shear stress and shear rate of a fluid. Viscosity is typically affected by temperature, chemical properties, and other constituents in the oil. Viscosity influences the oil's ability to flow which in-turn influences the motivating force, or pressure, required to push the oil sufficiently to develop the necessary flow. For example, hot oil flows faster than cold oil, which can influence operating pressure characteristics of the system. The rate of oil flow is important to the life of an engine. Previously, engine oil viscosity was of interest only to provide good hydrodynamic lubrication of load-bearing surfaces and to assure adequate flow throughout the engine. With recent advancements in engine controls that use engine oil for precise timing, oil viscosity has become increasingly important. Such advancements include cam phasing, active fuel management, and two-step valve actuation. These are all positive displacement devices that require an oil flow source to develop sufficient pressure which provides hydraulic actuation of components within an engine. Thus, their function can be sensitive to the viscosity characteristics of the oil. Engine oil viscosity can be difficult to forecast due to the variability of oil change intervals associated with driving conditions as well as various oil chemistries, and aftermarket oil additives.
Providing a control system to diagnose the viscosity of the engine oil would enhance the operation of engine components that rely on the engine oil.